It is almost Easter, 1543, and an unseasonably bleak spring still encrusts Tudor London with snow and ice. The shivery harshness of the weather is matched by the political and religious climate. As Henry VIII veers back towards traditional beliefs and church practices, protestant reformers find themselves in jeopardy. Those close to the court pin their hopes on Catherine Parr (known to be sympathetic to their cause) becoming the king's sixth wife. In London's chaotic streets, hellfire fundamentalists curse heretics and prophesy the coming of the “end-time”. What will the new year, officially beginning on Easter Day, bring?

For Matthew Shardlake, the hunchbacked lawyer who has shrewdly sleuthed his way through CJSansom's earlier compulsively gripping Tudor murder mysteries - Dissolution (2003), Dark Fire (2004) and Sovereign (2006) - the answer is: another testing challenge to his powers of detection. Entering Lincoln's Inn on Easter Sunday morning, he discovers two law students staring in horror at the fountain in Gatehouse Court. Under the ice sheathing the crimsoned water in its basin is a corpse with a hideously gashed throat and an eerily peaceful expression on its drained white face.

Things turn even more sinister when it becomes apparent that people in high places are eager to conceal the outrage. Alarming reports of other outlandish atrocities follow: a labourer on the Southwark marshes left to expire in agony from an appallingly infected wound, an eminent physician found floating with his throat cut in a tidal pool near the mudbanks of Lambeth.

As a plot with a clutch of steel pulls you though dramatic twists and turns and vivid, knowledgeable, widely diverse scenes of Tudor life, you watch Shardlake discern a terrible pattern in the butchery. The victims (more of whom gruesomely accumulate as the story proceeds) are all one-time religious reformers who have defected. The killings, perpetrated in a seemingly unstoppable sequence, horribly simulate the torments inflicted on sinful mankind by the angels with trumpets who pour out the “seven vials of wrath” in the Book of Revelation. In an England convulsed by religious upheaval and terror, a maniac is working his way through the Apocalypse's repertoire of punitive deaths (from a polluted sore, in salt water, in fresh water, by fire, in darkness and excruciating pain, as a river dries up, and accompanied by an earthquake).

Shardlake's tracking down of the zealous psychotic makes for a terrific whodunnit read. Clues are cunningly laid in place from the opening pages. Suspects and false leads abound. Sansom plays fair but constructs his puzzle so craftily that only an exceptionally acute reader will solve this case before Shardlake does. As always with Sansom, too, there is far more to the book than a pungently atmospheric period mystery executed with grisly bravura.

At one point, the trail of the murderer leads Shardlake into the chapterhouse of Westminster Abbey where workmen are boarding up luridly painted frescoes of scenes from the Book of Revelation. Although these sadistic visions are being removed from view, the deranged cruelty emblazoned in them is now at large in the nation, Sansom's novel suggests. Years of theological turmoil have unleashed irrational savageries. In a London whose streetscapes are dominated by religious wreckage (abandoned churches, half-demolished monasteries, gutted ecclesiastical glories), sectarian power struggles rage, while the displaced and homeless and the sick now deprived of the solace of monastic hospitals fight to survive.

As psychopaths, fanatics and brutalised time-servers flourish, all the decent characters in this novel are under strain. Besides the ordeals of the investigation, Shardlake has to cope with upsets in his emotional life. The marriage of his assistant, Barak, is buckling after the loss of a child. His friend, the former monk physician Guy, is tormented by his feelings for a handsome apprentice. The position of Cranmer, Shardlake's ally in the quest for the killer, is precarious. In the prevailing atmosphere of scared wariness it seems apt that one of the most sympathetic figures should be a woman confined to Bedlam by agoraphobia.

All whodunnits rely on revelations. This one relies on the Book of Revelation as well, not only for its apocalypse-themed slaughterings but to underscore its counterpointing of religiously sanctioned barbarity with humane rationality - something as pertinent today as to the Tudors.

Revelation by CJ Sansom
Macmillan £17.99 pp549

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